Tohoku J. Exp. Med., 2002, 196 (3)

Influence of Aging on the Carcinogen-Induced Protein Kinase
Activity in Rat Liver Cell Nuclei

TETSUO SAKAI, RITSUKO SATO, HITOSHI MIZUNO, HIDEO MATSUO,
AKIRA NOMURA, SHUNHAN KOH, HIDEKI GONDO and AKIRA WAKIZAKA

Department of Biochemistry, Kyorin University School of Medicine, Tokyo 181-8611

A carcinogen-induced increase in a protein kinase activity was found in cell nuclei of rat liver. The enzyme was extracted from isolated nuclei with a hypotonic buffer, retained to an anion-exchange column, eluted with 0.15 M NaCl containing solution and to be measured for the activity with casein as the substrate, showing a nature of a casein kinase. The change in the activity during the course of aging was studied with 5-, 10-, and 50-week old Wistar male rats. The activity was highest in 5-week-old rat but decreased in 10- and 50-week-old animal. A hepatocarcinogen, thioacetamide, induced an increase in activity in 10-week old rats but rather decreased in 5- and 50-week-old rats. Aging suppresses the activity of this unique enzyme. Thioacetamide abolishes this suppression resulting in an increase in the activity of the enzyme at a certain stage of aging.

Keywords —— aging; carcinogen; cell nucleus; protein kinase; thioacetamide

© 2002 Tohoku University Medical Press

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Tohoku J. Exp. Med., 2002, 196, 131-138

Address for reprints: Tetsuo Sakai, Department of Biochemistry, Kyorin University School of Medicine, 6-20-2 Shinkawa, Mitaka, Tokyo 181-8611, Japan.

e-mail: wakizaka@kyorin-u.ac.jp